"This past week I have spent in reflective thought, prayer and deep sorrow," she wrote in a message posted to Twitter on Monday. "I join my daughter in extending my help and services to all those affected by the diabolical act of terror which occurred in Manchester!"

"My heart goes out to all the victims: those who lost their lives, those injured, those recovering & all survivors of that night, along with the families & friends whose grief knows no bounds," her tribute continued. "I stand with you all in the face of evil & we stand together to never let it rule our lives."

"Thank you to all those who helped in any way that night in Manchester," she concluded. "I continually thank those who are & were in service protecting our freedoms every day all over the world. #MemorialDay."

Joan was backstage at the show when then bomb went off, and helped fans to safety by escorting them backstage immediately after the explosion. A source tells ET that the 23-year-old singer's mom worked tirelessly to help fans out of harm's way amid the chaos.